U.S. patent application number 11/026038 was filed with the patent office on 2005-07-21 for fuel injection control device for internal combustion engine.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Hashima, Takashi, Ichise, Masaharu, Kashiwagura, Toshimi, Nogawa, Shinichiro.
Application Number | 20050155578 11/026038 |
Document ID | / |
Family ID | 34616923 |
Filed Date | 2005-07-21 |
United States Patent
Application |
20050155578 |
Kind Code |
A1 |
Ichise, Masaharu ; et
al. |
July 21, 2005 |
Fuel injection control device for internal combustion engine
Abstract
An internal combustion engine (10) is provided with a port
injector (28) and an in-cylinder injector (22). Before a port
injection is started, the total amount of fuel to be injected is
calculated (at an injection amount calculation timing). The port
injection fuel amount and the in-cylinder injection fuel amount are
calculated by appropriately dividing the total amount between them.
If a change of the operating load on the internal combustion engine
(10) is detected after the injection amount calculation timing, the
load change is reflected in the amount of fuel to be injected in
the current engine cycle by increasing or decreasing the
in-cylinder injection fuel amount.
Inventors: |
Ichise, Masaharu;
(Susono-shi, JP) ; Kashiwagura, Toshimi;
(Susono-shi, JP) ; Nogawa, Shinichiro;
(Mishima-shi, JP) ; Hashima, Takashi;
(Gotenba-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
34616923 |
Appl. No.: |
11/026038 |
Filed: |
January 3, 2005 |
Current U.S.
Class: |
123/431 |
Current CPC
Class: |
F02D 41/3094 20130101;
F02D 41/401 20130101; Y02T 10/44 20130101; F02D 41/1498 20130101;
F02D 41/10 20130101; Y02T 10/40 20130101 |
Class at
Publication: |
123/431 |
International
Class: |
F02B 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 16, 2004 |
JP |
2004-009781 |
Claims
1. A fuel injection control device for an internal combustion
engine, comprising: operating load detecting means for detecting an
operating load on the internal combustion engine; a port injector
for port injection; an in-cylinder injector for in-cylinder
injection; fuel amount calculating means for calculating a port
injection amount of fuel to be injected from the port injector and
a reference in-cylinder injection amount of fuel to be injected
from the in-cylinder injector at a predetermined injection amount
calculation timing based on the operating load; port injection
control means which starts a port injection before an in-cylinder
injection so as to inject said port injection amount of fuel from
the port injector; correction fuel amount calculation means which
calculates a fuel correction amount for a change of the operating
load on the internal combustion engine if the change is detected
after the injection amount calculation timing and before a
reflection limit timing until which the amount of fuel to be
injected from the in-cylinder injector; and in-cylinder injection
control means which executes the in-cylinder injection after the
port injection so as to inject an amount of fuel from the
in-cylinder injector wherein the amount of fuel is determined based
on the reference in-cylinder injection amount and the correction
amount.
2. A fuel injection control device for an internal combustion
engine according to claim 1, wherein the in-cylinder injection
control means includes normal in-cylinder injection means which
starts a normal in-cylinder injection at a predetermined timing so
as to inject the reference in-cylinder injection amount of fuel if
a non-zero value is calculated as the reference in-cylinder
injection amount; and the correction fuel amount calculation means
includes normal in-cylinder injection amount correcting means which
increases or decreases the amount of fuel to be injected by the
normal in-cylinder injection by the correction amount of fuel
corresponding to a change of the operating load on the internal
combustion engine if the change is detected before a limit timing
until which the amount of fuel to be injected by the normal
in-cylinder injection can be changed.
3. A fuel injection control device for an internal combustion
engine according to claim 1, wherein the in-cylinder injection
control means includes normal in-cylinder injection means which
starts a normal in-cylinder injection at a predetermined timing so
as to inject the reference in-cylinder injection amount of fuel if
a non-zero value is calculated as the reference in-cylinder
injection amount; and the correction fuel amount calculation means
includes in-cylinder injection amount increasing means which
executes an additional in-cylinder injection so as to inject the
correcting amount of fuel corresponding to an increase of the
operating load on the internal combustion engine if the increase is
detected after a limit timing until which the amount of fuel to be
injected by the normal in-cylinder injection can be changed.
4. A fuel injection control device for an internal combustion
engine according to claim 1, wherein the in-cylinder injection
control means includes additional in-cylinder injection means which
executes an in-cylinder injection after the port injection so as to
inject the correcting amount of fuel corresponding to an increase
of the operating load on the internal combustion engine if the
increase is detected after zero is calculated as the reference
in-cylinder injection amount.
5. A fuel injection control device for an internal combustion
engine according to claim 1, wherein the fuel amount calculating
means includes: port fuel deviation estimating means which
estimates a deviation of the amount of fuel which actually enters a
cylinder from an intake port from an ideal amount of fuel which
should enters the cylinder from the intake port, based on the
change of the load on the internal combustion engine; and reference
amount correcting means which increases or decreases the reference
in-cylinder injection amount so as to compensate for the
deviation.
6. A fuel injection control device for an internal combustion
engine, comprising: an operating load detecting unit for detecting
an operating load on the internal combustion engine; a port
injector for port injection; an in-cylinder injector for
in-cylinder injection; a fuel amount calculating unit for
calculating a port injection amount of fuel to be injected from the
port injector and a reference in-cylinder injection amount of fuel
to be injected from the in-cylinder injector at a predetermined
injection amount calculation timing based on the operating load; a
port injection control unit which starts a port injection before an
in-cylinder injection so as to inject said port injection amount of
fuel from the port injector; a correction fuel amount calculation
unit which calculates a fuel correction amount for a change of the
operating load on the internal combustion engine if the change is
detected after the injection amount calculation timing and before a
reflection limit timing until which the amount of fuel to be
injected from the in-cylinder injector; and an in-cylinder
injection control unit which executes the in-cylinder injection
after the port injection so as to inject an amount of fuel from the
in-cylinder injector wherein the amount of fuel is determined based
on the reference in-cylinder injection amount and the correction
amount.
7. A fuel injection control device for an internal combustion
engine according to claim 6, wherein the in-cylinder injection
control unit includes a normal in-cylinder injection unit which
starts a normal in-cylinder injection at a predetermined timing so
as to inject the reference in-cylinder injection amount of fuel if
a non-zero value is calculated as the reference in-cylinder
injection amount; and the correction fuel amount calculation unit
includes a normal in-cylinder injection amount correcting unit
which increases or decreases the amount of fuel to be injected by
the normal in-cylinder injection by the correction amount of fuel
corresponding to a change of the operating load on the internal
combustion engine if the change is detected before a limit timing
until which the amount of fuel to be injected by the normal
in-cylinder injection can be changed.
8. A fuel injection control device for an internal combustion
engine according to claim 6, wherein the in-cylinder injection
control unit includes a normal in-cylinder injection unit which
starts a normal in-cylinder injection at a predetermined timing so
as to inject the reference in-cylinder injection amount of fuel if
a non-zero value is calculated as the reference in-cylinder
injection amount; and the correction fuel amount calculation unit
includes an in-cylinder injection amount increasing unit which
executes an additional in-cylinder injection so as to inject the
correcting amount of fuel corresponding to an increase of the
operating load on the internal combustion engine if the increase is
detected after a limit timing until which the amount of fuel to be
injected by the normal in-cylinder injection can be changed.
9. A fuel injection control device for an internal combustion
engine according to claim 6, wherein the in-cylinder injection
control unit includes an additional in-cylinder injection unit
which executes an in-cylinder injection after the port injection so
as to inject the correcting amount of fuel corresponding to an
increase of the operating load on the internal combustion engine if
the increase is detected after zero is calculated as the reference
in-cylinder injection amount.
10. A fuel injection control device for an internal combustion
engine according to claim 6, wherein the fuel amount calculating
unit includes: a port fuel deviation estimating unit which
estimates a deviation of the amount of fuel which actually enters a
cylinder from an intake port from an ideal amount of fuel which
should enters the cylinder from the intake port, based on the
change of the load on the internal combustion engine; and a
reference amount correcting unit which increases or decreases the
reference in-cylinder injection amount so as to compensate for the
deviation.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a fuel injection control
device for an internal combustion engine and, more particularly, to
a fuel injection control device for an internal combustion engine
which is provided with a port injector to inject fuel into the
intake port and an in-cylinder injector to inject fuel into the
cylinder.
[0003] 2. Background Art
[0004] As conventional internal combustion engines, those
comprising a port injector to inject fuel into the intake port and
an in-cylinder injector to inject fuel into the cylinder are known
as disclosed in, for example, Japanese Patent Laid-open No.
2003-13784. In such a prior art internal combustion engine
operating under certain conditions, port injection by a port
injector is combined with in-cylinder injection by an in-cylinder
injector so as to form a fuel-rich layer near the spark plug while
introducing uniform mixture into the cylinder. According to this
fuel injection technique, it is possible to keep lean the air-fuel
ratio of the mixture while producing stable combustion in the
cylinder. Hereinafter, such an internal combustion engine is
denoted as a "dual-injector type internal combustion engine".
[0005] In a dual-injector type internal combustion engine which
concurrently performs both port injection and in-cylinder
injection, the injection ratio between them must be controlled to
an appropriate value. Conventionally, such an internal combustion
engine therefore determines both the port injection fuel amount and
the in-cylinder injection fuel amount at a predetermined injection
amount calculation timing just before port injection is started.
Then, the internal combustion engine successively drives the port
injector and the in-cylinder injector so as to implement port and
in-cylinder fuel injections of the determined respective amounts.
According to this control technique, fuel can be injected into the
intake port and the cylinder at an appropriate ratio, allowing
stable combustion with a lean air-fuel mixture.
[0006] Including the above-mentioned document, the applicant is
aware of the following documents as a related art of the present
invention.
[0007] [Patent Document 1] Japanese Patent Laid-open No.
2003-13784
[0008] [Patent Document 2] Japanese Patent Laid-open No.
11-182283
[0009] [Patent Document 3] Japanese Patent Laid-open No.
5-231221
[0010] [Patent Document 4] Japanese Patent Laid-open No.
11-303669
[0011] In the above-mentioned prior art internal combustion engine,
however, the port injection fuel amount and the cylinder injection
fuel amount are calculated only once per engine cycle just before
port injection is started. Therefore, if the load on the internal
combustion engine changes or the change is detected after the
calculation, the load change is not reflected in the fuel injection
amount until the next engine cycle. More specifically, in the
above-mentioned prior art internal combustion engine, any change in
the load (intake air flow) during actual air intake, which may
occur after the fuel injection amount is calculated and just before
the port injection (intake stroke) is started, is not reflected in
the fuel injection amount.
[0012] If the load change is not reflected in the fuel injection
amount, no large change occurs in the torque of the internal
combustion engine. This means that the conventional dual-injector
type internal combustion engines leave room for improvement in
terms of response to load changes.
SUMMARY OF THE INVENTION
[0013] The present invention has been made to solve the
above-mentioned problem. It is an object of the present invention
to provide a fuel injection control device which enables an
internal combustion engine to make excellent responses to load
changes.
[0014] The above object is achieved by a fuel injection control
device for an internal combustion engine. The control device
includes an operating load detecting unit for detecting an
operating load on the internal combustion engine. A port injector
is provided for port injection. An in-cylinder injector is provided
for in-cylinder injection. The control device also includes a fuel
amount calculating unit for calculating a port injection amount of
fuel to be injected from the port injector and a reference
in-cylinder injection amount of fuel to be injected from the
in-cylinder injector at a predetermined injection amount
calculation timing based on the operating load. The control device
further includes a port injection control unit which starts a port
injection before an in-cylinder injection so as to inject said port
injection amount of fuel from the port injector. There is also
provided a correction fuel amount calculation unit which calculates
a fuel correction amount for a change of the operating load on the
internal combustion engine if the change is detected after the
injection amount calculation timing and before a reflection limit
timing until which the amount of fuel to be injected from the
in-cylinder injector. There is further provided an in-cylinder
injection control unit which executes the in-cylinder injection
after the port injection so as to inject an amount of fuel from the
in-cylinder injector wherein the amount of fuel is determined based
on the reference in-cylinder injection amount and the correction
amount.
[0015] Other objects and further features of the present invention
will be apparent from the following detailed description when read
in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 is a diagram for explaining the configuration of a
first embodiment of the present invention;
[0017] FIGS. 2A to 2D are diagrams for explaining the fuel
injection patterns used in the first embodiment of the present
invention;
[0018] FIG. 3 is a flowchart of an injection amount calculation
routine which is executed in the first embodiment of the present
invention;
[0019] FIG. 4 is a flowchart of a fuel injection routine which is
executed in the first embodiment of the present invention;
[0020] FIGS. 5A to 5C are timing charts for explaining how the
cylinder injection fuel amount is calculated in a second embodiment
of the present invention; and
[0021] FIG. 6 is a flowchart for explaining a processing sequence
which is executed in the second embodiment of the present invention
in place of step 106 in FIG. 3.
BEST MODE FOR CARRYING OUT THE INVENTION FIRST EMBODIMENT
System Configuration of First Embodiment
[0022] FIG. 1 is provided to explain the configuration of a first
embodiment of the present invention. As shown in FIG. 1, this
system embodiment has an internal combustion engine 10. The
internal combustion engine 10 is communicated with an intake port
12 and an exhaust port 14. An intake valve 16 is provided between
the intake port 12 and the in-cylinder space of the internal
combustion engine 10. An exhaust valve 18 is provided between the
exhaust port 14 and the in-cylinder space of the internal
combustion engine 10.
[0023] In addition, a spark plug 20 and an in-cylinder injector
(DInj) 22 for direct injection into the cylinder are set to the
internal combustion engine 10. The tip of the spark plug 20 is
exposed in the middle of the in-cylinder space. The tip of the
in-cylinder injector 22 is directed toward the center of the
in-cylinder space. The piston 24 of the internal combustion engine
10 has a cavity 26 formed on its top surface. Fuel, injected from
the in-cylinder injector 22 at a predetermined timing, is reflected
by the wall of the cavity 26 to form a gas layer near the tip of
the spark. Thus, the in-cylinder injector 22 generates a rich
mixture only near the spark plug 20, making it possible to secure
stable operation with a smaller amount of fuel, that is, realize
what is called stratified operation.
[0024] A port injector 28 is set to the intake port 12. The port
injector 28 can inject fuel into the intake port 12. Injecting fuel
into the intake port 12 makes it possible to introduce a uniformly
concentrated mixture into the cylinder. By combining port fuel
injection through the port injector 28 with in-cylinder fuel
injection through the in-cylinder injector 22 in a specific
operating region, the system of this embodiment can realize stable
operation with less fuel.
[0025] A throttle valve 30 is provided upstream of the intake port
12. The amount Ga of air which is taken into the internal
combustion engine 10 increases or decreases depending on the
opening degree of the throttle valve 30. Since the throttle valve
30 acts in conjunction with an accelerator pedal 32, the air intake
amount Ga can be adjusted by operating the accelerator.
[0026] As shown in FIG. 1, the system of this embodiment is
provided with an ECU (Electronic Control Unit) 40. The ECU 4.0 is
connected with a crank angle sensor 42, a revolution sensor 44, an
air flow meter 46 and other sensors. Based on the outputs of these
sensors, the ECU 40 can detect the crank angle CA, revolution speed
NE, intake air amount Ga of the internal combustion engine 10 and
the like. The ECU 40 is also connected with the above-mentioned
in-cylinder injector 22 and port injector 28. Based on the
operating condition of the internal combustion engine 10, detected
through the various sensors, the ECU 40 can drive these injectors
22 and 28 so as to make appropriate the port injection fuel amount
and the in-cylinder injection fuel amount.
Fuel Injection Patterns in First Embodiment
[0027] In the system of this embodiment, fuel injection is selected
from dual fuel injection performing both port injection and
in-cylinder injection (denoted as "port-in-cylinder injection"),
port-only fuel injection, etc. according to the operating condition
of the internal combustion engine 10. Referring to FIG. 2, the
following describes the fuel injection patterns used in this system
embodiment.
[0028] FIG. 2A is provided to explain an injection pattern which
occurs when port-in-cylinder injection is requested at the
injection amount calculation timing, then a change of the operating
load (namely, the intake air amount Ga) on the internal combustion
engine 10 is detected during the port injection period. In FIG. 2A,
the point "Injection Amount Calculation Timing" is a point of time
at which the port injection fuel amount and the in-cylinder
injection fuel amount are calculated for the internal combustion
engine 10.
[0029] In this embodiment, the injection amount calculation timing
differs depending on each cylinder. The injection amount
calculation timing for a cylinder is a predetermined point of time
which immediately precede the start of the combustion/expansion
stroke. At the point of time, the ECU 40 calculates a fuel
injection amount depending on the operating condition of the
internal combustion engine 10 and, further, calculates a port
injection fuel amount and a in-cylinder injection fuel amount so as
to divide the calculated fuel injection amount between port
injection and in-cylinder injection according to a predetermined
rule. Hereinafter, the in-cylinder injection fuel amount calculated
at this timing is specially referred to as the "reference
in-cylinder injection fuel amount".
[0030] In a port-only injection region, zero is obtained as the
reference in-cylinder injection fuel amount. In FIG. 2A, since the
example is a pattern for the region in which port-in-cylinder
injection should be done, a non-zero value is obtained at the
injection amount calculation timing as the reference in-cylinder
injection fuel amount.
[0031] In the system of this embodiment, the port injection period
is defined such that it roughly agrees with the period during which
the combustion/expansion stroke and exhaust stroke are done (the
360 CA.degree. period from the top dead center of compression to
the top dead center of exhaust) as shown in FIG. 2A. Depending on
the operating condition of the internal combustion engine 10, an
appropriate point of time is set in the port injection period by
the ECU 40 as the port injection time. At this port injection time,
the amount of fuel calculated as mentioned above is injected from
the port injector 28.
[0032] In the system of this embodiment, the normal cylinder
injection period is defined such that it roughly agrees with the
period during which the intake stroke is done (the 180 CA.degree.
period from the top dead center of exhaust to the bottom dead
center of intake). Depending on the operating condition of the
internal combustion engine 10, an appropriate point of time is set
in the normal in-cylinder injection period by the ECU 40 as the
normal in-cylinder injection time. At this normal in-cylinder
injection time, the in-cylinder injector 22 begins to inject the
reference in-cylinder injection amount of fuel calculated as
mentioned above.
[0033] Even after the injection amount calculation timing, the ECU
40 can correct the amount of fuel to be injected by the normal
in-cylinder injection until the normal in-cylinder injection is
started. Hereinafter, the deadline for this correction is referred
to as the "limit timing". In the example of FIG. 2A, since a load
change is detected earlier than the limit timing, the amount of
fuel to be injected by the normal in-cylinder injection can be
corrected according to the load change. Performing such a
correction improves the response of the internal combustion engine
10 and makes its air-fuel ratio control more accurate since a load
change which occurs after the injection fuel amount calculation
timing can be reflected in the total amount of fuel to be injected
in the current engine cycle.
[0034] As shown in FIG. 2A, therefore, if the operating load on the
internal combustion engine 10 changes between the injection fuel
calculation timing and the limit timing in this system embodiment,
a positive or negative correction is given to the reference
in-cylinder injection fuel amount in accordance with the load
change. The "Injection Amount Increase/Decrease Correction" in FIG.
2A indicates an instance of this correction timing. Since
correction is made in this manner, the system of this embodiment
can show excellent response to load changes which may occur between
the injection fuel calculation timing and the limit timing while
keeping high the air-fuel ratio control accuracy.
[0035] The total fuel injection amount determined at the injection
amount calculation timing can therefore be either increased or
decreased by correcting the amount of fuel to be injected by the
normal in-cylinder injection. According to the injection pattern
shown in FIG. 2A, even if the operating load changes after the
injection amount calculation timing, it is possible to inject an
appropriate amount of fuel according to the load change in the
current engine cycle regardless of whether the load change is
increases or decrease. The injection pattern shown in FIG. 2A is
effective for both increase and decrease in the load.
[0036] FIG. 2B is provided to explain an injection pattern which
occurs when port-in-cylinder injection is requested at the
injection amount calculation timing and then an increase of the
operating load on the internal combustion engine 10 is detected
after the normal in-cylinder injection is started (after the limit
timing). In this case, since the change of the load on the internal
combustion engine 10 is detected later than the limit timing, this
change cannot be reflected in the amount of fuel to be injected by
the normal in-cylinder injection.
[0037] However, since the normal in-cylinder injection terminates
during the intake stroke, there remains some time which may allow
re-execution of an in-cylinder injection. If in-cylinder injection
is re-executed by using this time, the total amount of fuel to be
injected in the current engine cycle, determined at the injection
amount calculation timing, can be given a positive correction.
[0038] That is, even if the load on the internal combustion engine
10 changes later than the limit timing, as long as the change is
detected at a time from which another in-cylinder injection can be
completed before the ignition, although it is not possible to
correct the total fuel injection amount to a lower amount in the
current engine cycle, it is possible to correct the total fuel
injection amount to a higher amount. Hereinafter, the deadline for
executing another in-cylinder injection is referred to as the
"reflection limit timing".
[0039] Therefore, if a change or, more specifically, an increase in
the load on the internal combustion engine is detected between the
limit timing and the reflection limit timing, the system of this
embodiment executes another fuel injection so as to correct the
injection fuel amount according to the increase of the load.
Hereinafter, "additional in-cylinder injection" is used to refer to
such an in-cylinder injection, namely, an in-cylinder injection
that is done in order to correct the fuel injection amount in
accordance with a load increase that occurs after the injection
amount calculation timing.
[0040] In the example shown in FIG. 2B, port-in-cylinder injection
is requested at the injection amount calculation timing and then a
load increase is detected during the intake stroke. In this case,
since the load increase is detected earlier than the reference
limit timing, the ECU 40 can perform an additional in-cylinder
injection. The "Injection Amount Increase Correction" in FIG. 2B
indicates a timing at which the amount of fuel to be injected for
correction by the additional in-cylinder injection is set, that is,
the amount of fuel corresponding to the load increase is set for
correction.
[0041] Further, in an engine cycle which requires port-in-cylinder
injection, a certain period during the compression stroke is
defined as the "additional in-cylinder injection period" as shown
in FIG. 2B. Depending on the operating condition of the internal
combustion engine 10, an appropriate point of time is set in the
additional in-cylinder injection period by the ECU 40 as the
additional in-cylinder injection time. At this additional
in-cylinder injection time, the additional in-cylinder injection is
performed to inject the previously set amount of fuel. According to
the procedure described so far, if the load on the internal
combustion engine 10 increases between the limit timing and the
reflection limit timing, the load increase can be reflected in the
total amount of fuel to be injected in the current engine cycle.
Thus, the injection pattern shown in FIG. 2B makes it possible to
realize excellent response to such load increases while keeping
highly accurate air-fuel ratio control.
[0042] FIG. 2C is provided to explain an injection pattern which
occurs if port-only injection is requested at the injection amount
calculation timing and then an increase of the operating load on
the internal combustion engine 10 is detected during the port
injection period. If the load on the internal combustion engine 10
is detected as changed at such a timing, its change cannot be
reflected in the port injection fuel amount. However, if the load
change is an increase, it is possible to correct the fuel amount in
accordance with the load increase by performing an additional
in-cylinder injection after the port injection.
[0043] "Injection Amount Increase Correction" in FIG. 2C indicates
a timing at which the amount of fuel to be injected for correction
in accordance with the detected load increase is set. "Additional
Cylinder Injection Period" also in FIG. 2C is substantially
identical to the normal in-cylinder injection period shown in FIG.
2A. That is, if port-only injection is requested at the injection
amount calculation timing and then a load increase is detected
earlier than the above-mentioned limit timing, the system of this
embodiment sets an additional in-cylinder injection period which is
identical to the normal in-cylinder injection period shown in FIG.
2A. Then, according to the operating condition of the internal
combustion engine 10, the ECU 40 sets an appropriate point of time
in the additional in-cylinder injection period as the additional
in-cylinder injection time and performs the additional in-cylinder
injection at the additional in-cylinder injection time.
[0044] According to the above-mentioned procedure, if only port
injection is requested at the injection amount calculation timing
and then a load increase is detected earlier than the limit timing,
execution of a port injection can be followed by an in-cylinder
injection as if port-in-cylinder injection was requested. Thus, the
injection pattern shown in FIG. 2C makes it possible to realize
excellent response and excellent air-fuel ratio control accuracy in
a case where load increase occurs under such conditions that
port-only injection is requested.
[0045] FIG. 2D is provided to explain an injection pattern which
occurs if port-only injection is requested at the injection amount
calculation timing and then an increase of the operating load on
the internal combustion engine 10 is detected during the intake
stroke, that is, the load increase is detected later than a timing
at which a normal in-cylinder injection should be started. In this
case, immediately after the load change (increase) is detected,
"Injection Amount Increase Correction" is performed as shown in
FIG. 2D, that is, the amount of fuel for correction in accordance
with the load increase is set.
[0046] Further in this case, a period which continues until just
before the reflection limit timing is set as "Additional Cylinder
Injection Period" after "Injection Amount Increase Correction" is
done. Then, according to the operating condition of the internal
combustion engine 10, the ECU 40 sets an appropriate point of time
in the additional in-cylinder injection period as the additional
in-cylinder injection time and performs the additional in-cylinder
injection at the additional in-cylinder injection time.
[0047] According to the above-mentioned procedure, if port-only
injection is requested at the injection amount calculation timing
and then a load increase is detected earlier than the reflection
limit timing, an in-cylinder injection can make up the fuel
shortfall left by the port injection. Thus, similar to the
injection pattern shown in FIG. 2C, this injection pattern in FIG.
2D makes it possible to realize excellent response and excellent
air-fuel ratio control accuracy in a case where load increase
occurs under such conditions that port-only injection is
requested.
Practical Processing in First Embodiment
[0048] The ECU 40 implements the aforementioned fuel injection
patterns by executing the routines shown in FIGS. 3 and 4. The
following will describe the details of these routines step by step.
FIG. 3 is a flowchart of an injection amount calculation routine
which is executed by the ECU 40 in order to calculate the amount of
fuel to be injected by the port injection, the amount of fuel to be
injected by the normal in-cylinder injection and the amount of fuel
to be injected by the additional in-cylinder injection.
[0049] The routine shown in FIG. 3 is activated periodically, for
example, every 1 msec. If this routine is activated, the operating
condition of the internal combustion engine 10, namely the engine
revolution speed NE and the engine load are detected at first based
on the individual sensor outputs (step 100). Then, the location of
the current timing in the current cycle of the internal combustion
engine 10 is detected. Specifically, the current crank angle CA of
the internal combustion engine 10 is detected (step 102).
[0050] Then, based on the detected crank angle CA, it is judged
whether the current timing is earlier than the injection amount
calculation timing (step 104). The crank angle which corresponds to
the deadline for performing an additional in-cylinder injection,
namely the reflection limit timing, is stored in the ECU 40. The
crank angle which corresponds to the injection amount calculation
timing is also stored in the ECU 40. By comparing these crank
angles with the current crank angle, this step 104 judges whether
the current timing is later than the reflection limit timing but
earlier than the injection amount calculation timing. If the
condition is true, the judgment result is "Before Injection Amount
Calculation Timing".
[0051] If the judgment result in the above-mentioned step 104 is
"Before Injection Amount Calculation Timing", a port injection fuel
amount and an in-cylinder injection fuel amount (reference
in-cylinder injection fuel amount) which are appropriate to the
current operating condition are calculated (step 106). Upon
completion of this step 106 processing, this activated routine is
immediately terminated. If the above processing is repeated, the
reference port injection fuel amount and the reference in-cylinder
injection fuel amount can be calculated as respective values that
are appropriate for the current operating condition at a timing of
injection amount calculation.
[0052] If the judgment result of the above-mentioned step 104 in
the routine of FIG. 3 is not "Before Injection Amount Calculation
Timing", it is judged whether port-only injection was requested at
the injection amount calculation timing (step 108). If the result
is that the requested injection is not port-only injection, it is
recognized that the requested injection is port-in-cylinder
injection. In this case, it is judged whether the current timing is
earlier than the limit timing (step 110).
[0053] If the judgment result of the above-mentioned step 110 is
"Before Limit Timing", the change of the load on the internal
combustion engine 10 can be reflected in the amount of fuel to be
injected by the normal in-cylinder injection. In this case, it is
judged at first whether the current load has increased from the
load which was detected at the injection amount calculation timing
(step 112). Practically, if the opening of the throttle shows a
meaningful increase, this step 112 judges that the load has
increased. If a load increase is recognized, the amount of fuel to
be injected by the normal in-cylinder injection is increased for
correction (step 114).
[0054] If any load increase is not recognized in the
above-mentioned step 112, it is judged whether the current load has
decreased from the load detected at the injection amount
calculation timing (step 116). Practically, if the opening of the
throttle shows a meaningful decrease, this step 116 judges that the
load has increased. If a load decrease is recognized, the amount of
fuel to be injected by the normal in-cylinder injection is
decreased for correction (step 118). If any load decrease is not
recognized, this activated routine is immediately terminated.
[0055] If it is judged in the above-mentioned step 108 that the
injection requested at the injection amount calculation timing is
port-only injection and in the above-mentioned step 110 that the
current timing is already later than the limit timing, it is judged
whether an additional in-cylinder injection is necessary.
Specifically, it is judged whether the current load (opening degree
of the throttle) shows a meaningful increase from the load (opening
degree of the throttle) detected at the injection amount
calculation timing (step 120).
[0056] If a load increase is recognized as the result of the
above-mentioned judgment, the amount of fuel to be injected by the
additional in-cylinder injection for correction is calculated (step
122). If no load increase is recognized in step 120, performing an
additional in-cylinder injection is judged to be not necessary. In
this case, this activated routine is terminated without doing any
processing to increase the amount of fuel to be injected.
[0057] According to the injection amount calculation routine
described so far, a port injection fuel amount and a reference
in-cylinder injection fuel amount, which are appropriate for the
current operating condition, can be calculated at the injection
amount calculation timing. In addition, if a load change is
detected before the limit timing under such conditions that
port-in-cylinder injection is requested, the amount of fuel to be
injected by the normal in-cylinder injection can be increased or
decreased for correction (refer to FIG. 2A). Likewise, if a load
increase is detected after the limit timing, the amount of fuel to
be injected by an additional in-cylinder injection can be
calculated (refer to FIG. 2B). Further, under such conditions that
port-only injection is requested, corrected fuel injection amount
which matches to a load increase detected after the injection
amount calculation timing can be calculated as fuel amount to be
injected by an additional in-cylinder injection (refer to FIG. 2C
and FIG. 2D).
[0058] FIG. 4 is a flowchart of a routine executed by the ECU 40 in
order to actually inject the amount of fuel, calculated by the
routine of FIG. 3, through port injection or in-cylinder injection.
The routine shown in FIG. 4 is repeatedly activated each time its
processing completes. If this routine is activated, the engine
rotation speed NE and the engine load are detected at first based
on the individual sensor outputs (step 130).
[0059] Then, based on the engine rotation speed NE and the engine
load, a port injection time and a normal in-cylinder injection time
are set (steps 132 and 134). Then, based on the current crank angle
CA, it is judged whether the port injection time has come (step
136). If it is judged that the port injection time has come,
processing for port injection is executed (step 138). Practically,
the port injector 28 is driven so as to inject the amount of fuel
calculated by the routine of FIG. 3.
[0060] Then, it is judged whether normal in-cylinder injection is
requested (step 140). In this step 140, it is judged that normal
in-cylinder injection is not requested if a non-zero value is set
by the routine of FIG. 3 as the amount of fuel to be injected by
the normal in-cylinder injection, that is, a non-zero value is
calculated at the injection amount calculation timing as the
reference in-cylinder injection fuel amount (refer to the
aforementioned step 106).
[0061] If it is judged in the above-mentioned step 140 that normal
in-cylinder injection is not requested, the routine jumps steps 142
and 144 described below. Otherwise, it is judged based on the
current crank angle whether the normal in-cylinder injection time
has come (step 142).
[0062] If the judgment result is that the normal in-cylinder
injection time has come, processing is executed in order to inject
a proper amount of fuel from the in-cylinder injector 22 (step
144). Practically, the in-cylinder injector 22 is driven so as to
inject the amount of fuel calculated last by the aforementioned
step 106, 114 or 118 of the routine shown in FIG. 3.
[0063] Then, in the routine shown in FIG. 4, it is judged whether
additional in-cylinder injection is requested (step 146). In this
step 146, it is recognized that additional in-cylinder injection is
requested if an amount of fuel to be injected by an additional
in-cylinder injection was calculated by the step 122 processing in
the routine of FIG. 3.
[0064] If a request for additional in-cylinder injection is
recognized, the in-cylinder injector 22 is driven so as to inject
the amount of fuel calculated by the above-mentioned step 122 for
correction (step 148). Meanwhile, if it is judged that no request
is recognized for additional in-cylinder injection, it is judged
based on the current crank angle whether the current timing is
earlier than the reflection limit timing (step 150).
[0065] If the current timing is judged to be earlier than the
reflection limit timing, the above-mentioned step 146 processing is
executed again since there remains the possibility that a request
for additional in-cylinder injection may occur in the current
engine cycle. Then, if the reflection limit timing comes without a
request for additional in-cylinder injection, the step 150 produces
a negative judgment, terminating the this activated routine.
[0066] As described so far, according to the routine shown in FIG.
4, if execution of a normal in-cylinder injection is requested, a
port injection can be followed by execution of a normal in-cylinder
injection. According to the routine of FIG. 3, when a normal
in-cylinder injection is started, load change is reflected in the
amount of fuel to be injected by the normal in-cylinder injection.
Thus, the system of this embodiment can implement the injection
pattern shown in FIG. 2A.
[0067] Moreover, according to the system of this embodiment,
corrected fuel amount that matches engine load increase is
calculated at step 120 shown in FIG. 3, if the engine load increase
is detected after the port injection and the normal in-cylinder
injection have done and before the reflection limit timing has
come. Then, if corrected fuel amount is calculated as described
above, the additional in-cylinder injection is executed for
injecting the corrected fuel amount by the routine shown in FIG. 4.
Thus, the system of this embodiment can implement the injection
pattern shown in FIG. 2B.
[0068] Further, in the system of this embodiment, if port-only
injection is requested at the injection fuel amount calculation
timing, the necessity of normal in-cylinder injection is negated
according to the routine shown in FIG. 4. Even in this case, after
the port injection, it is possible to immediately begin to judge
whether additional in-cylinder injection is necessary. If an engine
load increase is detected before the reflection limit timing, the
amount of fuel corresponding to the increase is calculated for
correction by step 120 in FIG. 3. In this case, an additional
in-cylinder injection can be executed to inject the corrected fuel
amount according to the routine shown in FIG. 4. Thus, the system
of this embodiment can implement the injection patterns shown in
FIGS. 2C and 2D.
[0069] As described so far, the system of this embodiment can
selectively implement an appropriate injection pattern, any of
those shown in FIG. 2A through FIG. 2D, according to the request
made at the injection amount calculation timing, and the timing at
which the load change is detected. Consequently, the system of this
embodiment can realize an internal combustion engine 10 capable of
showing excellent response to load changes and maintaining high
accuracy air-fuel ratio control.
[0070] Note that in the aforementioned first embodiment, when the
load on the internal combustion engine 10 is recognized as changed,
the amount of fuel to be injected is corrected in such a manner as
to improve not only the response to the load change but also the
air-fuel control accuracy. However, how to correct the injection
fuel amount is not limited to this manner. For example, correction
may be done so as to intentionally make richer the air-fuel ratio
if improvement of the response is given higher priority.
Second Embodiment
[0071] Referring to FIGS. 5 and 6, the following describes a second
embodiment of the present invention. In terms of hardware
configuration, the system of this embodiment is the same as that of
the first embodiment. That is, the system of this embodiment is
provided with both an in-cylinder injector 22 and a port injector
28 which are identical to those in the first embodiment.
Characteristics of Second Embodiment
[0072] In the internal combustion engine 10, some transport delay
occurs until fuel is introduced into the cylinder after the fuel is
injected from the port injector 28. Therefore, increasing or
decreasing the port injection fuel amount according to the change
of the engine load is not immediately reflected in the amount of
fuel to be injected into the cylinder from the intake port 12.
Consequently, in a transient period responding to a load increase,
the amount of fuel entering the cylinder from the intake port 12 is
smaller than the ideal value. Also in a transient period responding
to a load decrease, the mount of fuel entering the cylinder from
the intake port 12 is larger than the ideal value.
[0073] On the contrary, the fuel injected from the in-cylinder
injector 22 is supplied into the cylinder without transport delay.
Therefore, when the amount of fuel injected into the cylinder from
the intake port 12 is deficient, the in-cylinder injection fuel
amount can be increased so as to compensate for the deficiency.
Likewise, when the amount of fuel injected into the cylinder from
the intake port 12 is excessive, the in-cylinder injection fuel
amount can be decreased so as to compensate for the surplus. Using
this capability of the in-cylinder injector 22, the total injection
fuel amount can be controlled to an ideal value in each engine
cycle even during transient periods.
[0074] FIG. 5 is a timing chart for explaining an in-cylinder
injection fuel amount calculation method which is used to implement
the above-mentioned capability in this embodiment. More
specifically, FIG. 5A shows the waveform of the total requested
injection amount corresponding to load change. FIG. 5B shows the
waveform of the calculated port injection amount corresponding to
the transition of the total requested injection amount. FIG. 5C
shows the transition of the in-cylinder injection amount which
would occur following the transition of the total requested
injection amount (broken line) and the transition of the
in-cylinder injection amount which includes the amount of fuel
which compensates for the effect of the fuel transport delay (solid
line).
[0075] The amount of fuel which enters the cylinder from the intake
port 12 shows the largest transport delay effect immediately after
the total requested injection amount is changed. Then, the
transport delay effect decreases with time after the change occurs.
Therefore, the largest compensating fuel amount is given to the
in-cylinder injection amount when the total requested injection
amount is changed, and then the compensating fuel amount is
gradually reduced with time, as shown in FIG. 5C in the system of
this embodiment.
Practical Processing in Second Embodiment
[0076] FIG. 6 is a flowchart showing the flows of processing
executed by the ECU 40 in this embodiment in order to implement the
above-mentioned capability. These flows of processing are to
replace the processing of the step 106 in the routine of FIG. 3.
That is, this processing sequence is to be executed if step 104 in
the routine of FIG. 3 judges the current timing to be "Before
Injection Amount Calculation Timing".
[0077] In the processing sequence shown in FIG. 6, a total
requested injection amount is calculated at first based on the
operating condition and then a port injection fuel amount Qp and a
reference in-cylinder injection fuel amount QDB are calculated by
dividing the requested amount between them at a predefined ratio
(step 160). Then, it is judged whether this total requested
injection amount is greatly larger than the total requested
injection amount which was previously calculated by the routine
(whether an increase beyond a predefined value is recognized) (step
162).
[0078] If it is judged that the total requested injection amount
shows such a great increase, a request up flag is turned ON to
indicate a sharp increase in the engine load while a request down
flag is turned OFF (step 164). In addition, a compensation counter
C is cleared so as to be associated with the start of a transient
period (step 166).
[0079] On the contrary, if the aforementioned step 162 results in a
negative judgment, it is judged whether this total requested
injection amount is greatly smaller than the total requested
injection amount which was previously calculated by the routine
(whether a decrease beyond a predefined value is recognized) (step
168). If it is judged that the total requested injection amount
shows such a great decrease, the request down flag is turned ON to
indicate a sharp decrease in the engine load while the request up
flag is turned OFF (step 170). Since this time point is also a
start time of a transient period, the aforementioned processing of
step 166 is executed in order to clear the compensation counter
C.
[0080] If it is judged by the aforementioned step 168 that the
total requested injection amount does not show a sharp decrease,
processing goes to step 172 while maintaining the status of the
request up flag, that of the request down flag and the count value
of the compensation counter C. In step 172, the compensation
counter C is incremented. By the procedure described so far, the
elapsed time since the occurrence of a sharp change in the total
requested injection amount is measured by the compensation counter
C.
[0081] Then, in FIG. 6, a transport delay compensating value
.DELTA.Q.sub.(c) is calculated to compensate the port injection
fuel for the transport delay effect (step 174). The transport delay
compensating value .DELTA.Q(c) is a function of the magnitude of
the change in the total requested injection amount and the count
value of the compensation counter C. Practically, when the count
value of the compensation counter C is "1", that is, immediately
after a sharp change is detected in the total requested injection
amount by step 162 or 168, the ECU 40 calculates the initial value
of the transport delay compensating value .DELTA.Q.sub.(c) based on
the magnitude of the change detected in the total requested
injection amount. The initial value of .DELTA.Q.sub.(c) is set to
be larger as the requested amount changes bigger.
[0082] In addition, if the count value of the compensation counter
C is larger than "1", the ECU 40 calculates the transport delay
compensating value .DELTA.Q.sub.(c) by multiplying the
aforementioned initial value by an attenuation factor k. The
attenuation factor k is initially "1.0" and decreases at almost a
constant ratio each time the compensation counter C is increased
until it reaches to "0". Therefore, the transport delay
compensating value .DELTA.Q.sub.(c) gradually decreases to "0"
after the total requested injection amount shows a sharp
change.
[0083] After the transport delay compensating value
.DELTA.Q.sub.(c) is calculated, it is judged whether the request up
flag is ON (step 176). If the request up flag is ON, it is judged
that the transport delay effect is making insufficient the amount
of fuel which enters the cylinder. In this case, therefore, the
amount Q.sub.D of fuel to be injected by the normal in-cylinder
injection is obtained by adding the transport delay compensating
value .DELTA.Q.sub.(c) to the reference in-cylinder injection
amount Q.sub.DB (step 178).
[0084] If the result of the above-mentioned processing of step 176
indicates that the request up flag is not ON, it is judged that the
transport delay effect is making excessive the amount of fuel which
enters the cylinder. In this case, therefore, the amount Q.sub.D of
fuel to be injected by the normal in-cylinder injection is obtained
by subtracting the transport delay compensating value
.DELTA.Q.sub.(c) from the reference in-cylinder injection amount
Q.sub.DB (step 179).
[0085] In the system of this embodiment, the values obtained
according to the procedure of FIG. 6 are treated as the amount of
fuel to be injected by the port injection (port injection fuel
amount) and the amount of fuel to be injected by the normal
in-cylinder injection (reference in-cylinder injection fuel amount)
(see FIG. 3). Then, as described so far, the reference in-cylinder
injection fuel amount is changed by the processing sequence of FIG.
6 so as to compensate for the transport delay of the port-injected
fuel. That is, the corrected reference in-cylinder injection fuel
amount agrees with the solid line shown in FIG. 5C. In addition to
the capabilities of the first embodiment, therefore, this system
embodiment can effectively prevent the injection amount control
accuracy from deteriorating due to the fuel transport delay.
[0086] The major benefits of the present invention described above
are summarized as follows:
[0087] According to the first aspect of the present invention, in
an internal combustion engine provided with aport injector and an
in-cylinder injector, if the operating load on the internal
combustion engine changes after the injection amount calculation
timing, it is possible to calculate a correction amount of fuel
corresponding to the change. By reflecting the correction amount in
the cylinder injection amount, the load change can quickly be
reflected in the injection fuel amount. Thus, the present invention
can raise the response of the internal combustion engine.
[0088] According to the second aspect of the present invention, if
a change of the operating load on the internal combustion engine is
detected after the injection amount calculation timing and before a
limit timing until which the amount of fuel to be injected by the
normal in-cylinder injection can be changed, the amount of fuel to
be injected by the normal cylinder injection can be increased or
decreased. In this case, both the increase and decrease in the
operating load can be reflected in the fuel injection amount.
[0089] According to the third aspect of the present invention, if
an increase of the operating load on the internal combustion engine
is detected after the limit timing until which the amount of fuel
to be injected by the normal in-cylinder injection can be changed,
a cylinder injection can be executed after the normal cylinder
injection so as to inject the correcting amount of fuel
corresponding to the increase. Thus, the present invention can
raise the response at acceleration.
[0090] According to the fourth aspect of the present invention,
even if zero is calculated as the reference cylinder injection
amount at the injection amount calculation timing and an increase
of the operating load on the internal combustion engine is detected
later, a cylinder injection can be executed to inject a correction
amount of fuel corresponding to the increase. Thus, the present
invention can raise the response at acceleration.
[0091] According to the fifth aspect of the present invention, the
deviation of the amount of fuel which actually enters the cylinder
from the intake port from the ideal amount can be estimated based
on the change of the load on the internal combustion engine. The
reference cylinder injection amount can be increased or decreased
so as to cancel the deviation. In this case, the error of the
amount of fuel that enters the cylinder from the port due to the
transport delay can be compensated for by the amount of fuel to be
injected from the in-cylinder injector. Thus, the present invention
can accurately control the injection amount during transient
periods. Further, the present invention is not limited to these
embodiments, but variations and modifications may be made without
departing from the scope of the present invention.
* * * * *